Studies are underway to apply a non-contiguous band transmission in addition to a contiguous band transmission to an uplink of LTE-Advanced, which is the development product of 3rd Generation Partnership Project Long Term Evolution (3GPP LTE), in order to improve sector throughput.
As shown in FIG. 1A, the contiguous band transmission is a technique used to allocate a transmission signal of one terminal to the contiguous frequency band. Meanwhile, as shown in FIG. 1B, the non-contiguous band transmission is a technique used to allocate a transmission signal of one terminal to non-contiguous frequency bands. Compared to the contiguous band transmission, the non-contiguous band transmission enhances flexibility of allocating the transmission signal of each terminal to the frequency band, and thus may obtain a larger frequency scheduling effect.
In LTE-Advanced, limiting the maximum number of clusters (i.e., contiguous band block or a unit) in the non-contiguous bands to two has been studied, in order to decrease the number of signaling bits of frequency resource allocating information that is reported from a base station to a terminal.
In the non-contiguous band allocation of LTE-Advanced, allocating a frequency resource to the terminal in a frequency unit referred to as an RB Group (RBG), which includes a plurality of RBs (Resource Blocks: 1RB=180 kHz), has been studied. The technique disclosed in non-patent literature 1 is known as a method of reporting RBG that the base station allocates to the terminal.
Non-patent literature 1 discloses that, in order to perform the non-contiguous band allocation, the base station converts a start RBG index and an end RBG index of each cluster to be allocated to the terminal into notification information r (i.e., combinatorial index) calculated by equation 1 and notifies the terminal of the result.
                    [        1        ]                                                                                  r            =                                          ∑                                  i                  =                  0                                                                      2                    ⁢                    M                                    -                  1                                            ⁢                              〈                                                                                                                              N                          rb                                                -                        b                                                                                                                                                                          2                          ⁢                          M                                                -                        i                                                                                            〉                                              ,                      r            ∈                          {                              0                ,                …                ⁢                                                                  ,                                                      (                                                                                                                        N                            rb                                                                                                                                                                            2                            ⁢                            M                                                                                                                )                                    -                  1                                            }                                      ⁢                                  ⁢                              in            ⁢                                                  ⁢            which            ⁢                                                  ⁢                          〈                                                                    x                                                                                        y                                                              〉                                =                      {                                                                                                      (                                                                                                    x                                                                                                                                y                                                                                              )                                        =                                          C                      y                                                                                                                  x                                                                                                                                                                                      x                    ≥                    y                                                                                                0                                                                      x                    <                    y                                                                                                          (                  Equation          ⁢                                          ⁢          1                )            
Nrb indicates the total number of RBGs, and M indicates the number of clusters. Also, b1 indicates the i-th element of an information sequence in which the start and the end RBG indices of the clusters are arranged in order of cluster indices, which includes a start
RBG index si and an end RBG index ei, i, e., an RGB index indicating a start or end position of cluster band, where i={0, 1, . . . , 2M−2, 2M−1} holds true as for cluster index i, and is defined as below.bi=si/2 (when i is an even number)bi=e(i−1)/2 (when i is an odd number)
In other words, bi={b0, b1, . . . , b2M−2, b2M−1}={s0, e0, s1, e1, . . . sM−1, eM−1} holds true. As shown in equation 2, si and ei which are components of bi are defined in ascending order using different integers as shown in equation 2. According to this definition, the terminal can uniquely derive 2M RBG indices (bi) from the reported notification information r.si<ei<si+1<ei+1   (Equation 2)
Since “r” in equation 1 includes components corresponding to the number of combinations to select different 2M from Nrb, the number of necessary signaling bits L is represented by equation 3.
                    [        2        ]                                                            L        =                  ⌈                                    log              2                        ⁡                          (                                                                                          N                      rb                                                                                                                                  2                      ⁢                      M                                                                                  )                                ⌉                                    (                  Equation          ⁢                                          ⁢          3                )            
FIG. 2 shows the numbers of signaling bits Ls, which is calculated by equation 3, at Nrb=25RBG and Nrb=50RBG in the case of M=2.